The removal of H.sub.2 S from a liquid or gaseous hydrocarbon stream is a problem that has challenged many workers in many industries. One such industry is the petroleum industry, where the H.sub.2 S content of certain crudes from reservoirs in many areas of the world is too high for commercial acceptance. The same is true of many natural gas streams. Even where a crude or gas stream contains only a minor amount of sulfur, the processes to which the crude oil or fractions thereof are subjected often produce one or more hydrocarbon streams that contain H.sub.2 S.
The presence of H.sub.2 S in hydrocarbon streams presents many environmental and safety hazards. Hydrogen sulfide is highly flammable, toxic when inhaled, and strongly irritates the eyes and other mucous membranes. In addition, sulfur-containing salts can deposit in and plug or corrode transmission pipes, valves, regulators, and the like. Flaring of natural gas that contains H.sub.2 S does not solve the problem for gas streams because, unless the H.sub.2 S is removed prior to flaring, the combustion products will contain unacceptable amounts of pollutants, such as sulfur dioxide (SO.sub.2)--a component of "acid rain."
Hydrogen sulfide has an offensive odor, and natural gas containing H.sub.2 S often is called "sour" gas. Treatments to reduce or remove H.sub.2 S from hydrocarbon or other substrates often are called "sweetening" treatments. The agent that is used to remove or reduce H.sub.2 S levels sometimes is called a "scavenging agent."
The problem of removing or reducing H.sub.2 S from hydrocarbon substrates has been solved in many different ways in the past. Most of the known techniques involve either (a) absorption, or selective absorption by a suitable absorbent, after which the absorbent is separated and the sulfur removed to regenerate and recycle the absorbent, or (b) selective reaction with a reagent that produces a readily soluble product. A number of known systems treat a hydrocarbon stream with an amine, an aldehyde, an alcohol, and/or a reaction product thereof.
Previously known sulfhydryl scavengers theoretically may require about 2-3 ppm of scavenger per ppm of hydrogen sulfide; however, the amount actually required is much higher--in the range of about 5-10 or more ppm per ppm of hydrogen sulfide. A high amount of scavenger is required because of the difficulty of distributing the scavenger evenly throughout the fluid. Much of this difficulty is the result of inadequate solubility of the scavenger in the hydrocarbon substrate.
A continuing need exists for effective and efficient processes and compositions to reduce and/or remove sulfhydryl compounds from hydrocarbon substrates.